Non-corrosive cleaning method for use in the manufacture of microelectronic device

ABSTRACT

A method for use in the manufacture of a microelectronic device is set forth. The method includes a first step in which a workpiece including exposed aluminum metallized surfaces and residues is provided. The workpiece, including the exposed aluminum metallized surfaces, is then treated with an alkaline, water-based solution containing one or more components that form an aluminosilicate on the exposed aluminum metallized surfaces. The solution reacts with the residues and assists in removing them from the workpiece. Preferably, the solution is comprised of DI water, and ammonium hydroxide based component, such as TMAH, silicic acid, and aluminum hydroxide.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuaton of prior application U.S. Ser.No. 09/099,309, filed Jun. 18, 1998 now issued U.S. Pat. No. 5,980,643.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

The importance of clean semiconductor workpiece surfaces in thefabrication of semiconductor microelectronic devices has been recognizedfor a considerable period of time. Over time, as VLSI and ULSI siliconcircuit technology has developed, the cleaning processes have graduallybecome a particularly critical step in the fabrication process. It hasbeen estimated that over 50% of the yield losses sustained in thefabrication process are a direct result of workpiece contaminants. Traceimpurities, such as sodium ions, metals, and particles, are especiallydetrimental if present on semiconductor surfaces during high-temperatureprocessing because they may spread and diffuse into the semiconductorworkpiece and thereby alter the electrical characteristics of thedevices formed in the workpiece. Similar requirements are placed onother such items in the electronics industry, such as in the manufactureof flat panel displays, hard disk media, CD glass, and other suchworkpieces.

Cleaning of a semiconductor workpiece, and other electronic workpieces,occurs at many intermediate stages of the fabrication process. Cleaningof the workpiece is often critical after, for example, photoresiststripping and/or ashing. This is particularly true where the strippingand/or ashing process immediately proceeds a thermal process. Completeremoval of the ashed photoresist or the photoresist/stripper isnecessary to insure the integrity of subsequent processes.

The actual stripping of photoresist from the workpiece is yet anotherfabrication process that is important to integrated circuit yield, andthe yield of other workpiece types. It is during the stripping processthat a substantial majority of the photoresist is removed or otherwisedisengaged from the surface of the semiconductor workpiece. If thestripping agent is not completely effective, photoresist may remainbonded to the surface. Such bonded photoresist may be extremelydifficult to remove during a subsequent cleaning operation and therebyimpact the ability to further process the workpiece.

Various techniques are used for stripping photoresist from thesemiconductor workpiece. Mixtures of sulfuric acid and hydrogen peroxideat elevated temperatures are commonly used. However, such mixtures areunsuitable for stripping photoresist from wafers on which metals, suchas aluminum or copper, have been deposited. This is due to the fact thatsuch solutions will attack the metals as well as the photoresist.Solvent chemistries are often used after metal layers have beendeposited. In either case, limited bath life, expensive chemistries, andhigh waste disposal costs have made alternative strip chemistriesattractive.

Plasma stripping systems provide such an alternative and have been usedfor stripping both pre- and post-metal photoresist layers. Thisstripping technique, however, does not provide an ideal solution due tothe high molecular temperatures generated at the semiconductor workpiecesurface. Additionally, since photoresist is not purely a hydrocarbon(i.e., it generally contains elements other than hydrogen and carbon),residual compounds may be left behind after the plasma strip. Suchresidual compounds must then be removed in a subsequent wet clean.

As such, one of the more vexing problems in microelectronic devicefabrication, such as in the manufacture of semiconductor integratedcircuits, is the cleaning of workpieces having exposed metallization attheir surfaces. Frequently, such cleaning involves removal of residuesformed during the etching and plasma ashing processes associated withforming patterned metallization on the workpiece surface. These residuesare commonly called “polymers”, but also include inorganic compounds.

To date the most successful methods for removing these residues hasinvolved non-water based wet cleaner. These cleaners have mainlyinvolved hydroxylamine based reducing chemistries and have been found tobe quite effective and robust. The typical polymer removal process alsouses IPA as an intermediate rinse agent to eliminate corrosion thatcould happen in the final DI rinse if the amines in the residue removermixed directly with water. However, the semiconductor industry is beingdriven to eliminate or reduce the use of such chemistries because ofenvironmental regulations and cost concerns.

The present inventor has recognized that a water-based replacement forthese mixtures would have many advantages over the non-water basedchemistries currently employed. This is due to the fact that high pHwater based solutions have the ability to dissolve many of the inorganiccompounds thought to exist in, for example, post etch residues. Examplesof such solutions include solutions of ammonium hydroxide ortetramethylanunonium hydroxide. While these solutions etch Ti and TiNfilms on the order of Angstroms per minute and are thus suitable for usewith such films, they etch aluminum films on the order of microns perminute and are thus not suitable for use with workpieces having exposedaluminum metallization. As such, the use of such solutions in residueremoval has not been explored in any significant manner.

BRIEF SUMMARY OF THE INVENTION

A method for use in the manufacture of a microelectronic device is setforth. The method includes a first step in which a workpiece includingexposed aluminum metallized surfaces and residues is provided. Theworkpiece, including the exposed aluminum metallized surfaces, is thentreated with an alkaline, water-based solution containing one or morecomponents that form an aluminosilicate on the exposed aluminummetallized surfaces. The solution reacts with the residues and assistsin removing them from the workpiece. Preferably, the solution iscomprised of DI water, and ammonium hydroxide based component, such asTMAH, silicic acid, and aluminum hydroxide.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a process flow diagram illustrating one embodiment of aprocess in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a process flow diagram illustrating one embodiment of aprocess for treating a workpiece, such as a semiconductor wafer,pursuant to manufacturing a microelectronic component, such as asemiconductor integrated circuit. As illustrated, the workpiece isprovided for processing at step 10. The workpiece is preferably in theform of a semiconductor wafer having aluminum interconnect metallizationthat is exposed at a surface of the workpiece. The surface also includesresidues that remain after prior processing. Such prior processing mayinclude plasma etching, plasma ashing, and/or photoresist strippingprocesses that generally leave polymer in inorganic compounds asresidues.

At step 20 of FIG. 1, the workpiece is brought into contact with analkaline, waterbased solution that is formulated to remove the residueswithout substantially attacking the aluminum metallization. Moreparticularly, the alkaline, water-based solution includes one or morecomponents that form an aluminosilicate film over the exposed surfacesof the aluminum metallization, which passivates the metallization andinhibits corrosion that would otherwise occur due to the alkaline natureof the solution. The workpiece and solution may be brought into contactwith one another using, for example, a Spray Acid Tool available fromSemitool, Inc., of Kalispell, Mont.

In accordance with a preferred solution composition, the solutionincludes DI water and an ammonium hydroxide based component, such astetramethylammonium hydroxide (TMAH). The ammonium hydroxide basedcomponent is used to render the solution alkaline. The solution furthercomprises small amount of silicic acid and aluminum hydroxide. Thesolution forms a passive aluminosilicate film that grows on the surfacesof the aluminum metallization. In this embodiment of the solution, thesilicic acid is the source of the silicon and the aluminum hydroxide isthe source of aluminum ions.

Experiments have been performed using various relative concentrations ofthe foregoing components. To this end, a 10 liter solution was formed byadding DI water to 35 cc of 25% weight TMAH, 48 grams of silicic acid,and 1.4 grams of aluminum hydroxide. Semiconductor wafers having exposedaluminum pads that were surrounded by residues, including oxides, wereused. A scanning profilometer was used to measure the step heightbetween the residues and the aluminum pads as well as the surfaceroughness of the pads. The solution was heated to 80 degrees Celsius andthe wafers were then exposed to the solution for approximately 10minutes. While the solution removed the residues, no significant pittingor corrosion of the aluminum pads was observed. Similar tests were alsoperformed with mixtures of 950 cc of DI water, 50 cc of ammoniumhydroxide, 4.8 grams of silicic acid, and 0.14 grams of aluminumhydroxide, with substantially the same results. Still further, solutionsusing NH₄OH instead of TMAH have also approved effective. In allinstances, no noticeable reduction in the sheet resistance of thealuminum metallization has been observed as a result of this treatment.

Lower concentrations of silicic acid are not as effective in passivatingthe exposed aluminum metallization. Preferably, the solution issubstantially saturated with silicic acid for more effectivepassivation.

In some instances, it may be desirable to include surfactants in thesolution. Such surfactants may assist in inhibiting particlere-deposition and, further, may unhibit roughenning of any exposedsilicon surfaces. For example, an amount of FC 93 and NCW 601 may beadded to the solution for this purpose.

The foregoing method can also be generalized for use with other metalsused for metallization, such as copper. To this end, a workpieceincluding exposed metallized surfaces of a metal X and further includingsurface residues is provided. The workpiece, including the exposedmetallized surfaces, is treated with an alkaline, water-based solutioncontaining one or more components that form a protective compound ofmetal X on the exposed metallized surfaces that prevents the metallizedsurfaces from substantial corrosion resulting from contact with thesolution. The alkaline nature of the solution assists in removing theresidues from the workpiece.

The foregoing alkaline, water-based solutions have substantial benefitsover the prior cleaning solutions. For example, water-based solutionstend to be more environmentally friendly and, as such, are generallycheaper to obtain, use, and dispose. Such solutions do not requirededicated drains or special waste disposal. Further, intermediate IPArinsing of the workpiece may, if desired, be eliminated when suchsolutions are used.

Numerous modifications may be made to the foregoing process withoutdeparting from the basic teachings thereof. Although the presentinvention has been described in substantial detail with reference to oneor more specific embodiments of the process and solution, those of skillin the art will recognize that changes may be made thereto withoutdeparting from the scope and spirit of the invention as set forth in theappended claims.

What is claimed is:
 1. A non-corrosive cleaning method for use in themanufacture of a microelectronic device comprising the steps of:providing a workpiece including exposed metallized surfaces comprisingaluminum, said exposed metallized surfaces having surface residues;treating said workpiece, including said exposed metallized surfaces,with a solution comprising an aluminum-containing constituent thesolution reacting at the exposed metallized surfaces to form ananti-corrosive film over said exposed metallized surfaces, said solutionfurther assisting in removal of said surface residues from saidworkpiece.
 2. A method as set forth in claim 1 wherein the surfaceresidues are organic residues.
 3. A method as set forth in claim 2wherein the solution is a water-based, alkaline solution.
 4. A method asset forth in claim 1 wherein the aluminum-containing constituentcomprises aluminum hydroxide.
 5. A method as set forth in claim 1wherein the solution further comprises a silicon-containing constituent.6. A method as set forth in claim 5 wherein the silicon-containingconstituent comprises silicic acid.
 7. The method of claim 5 whereinsaid solution forms a compound of aluminum and silicon at saidmetallized surfaces.
 8. A method as set forth in claim 1 wherein thesolution forms an aluminosilicate at the metallized surfaces.
 9. Amethod as set forth in claim 8 wherein the solution is a water-based,alkaline solution.
 10. A method as set forth in claim 9 wherein thesurface residues are organic residues.
 11. A non-corrosive cleaningmethod for use in the manufacture of a microelectronic device comprisingthe steps of: providing a workpiece including exposed metal surfacescomprising aluminum, said exposed metal surfaces having surfaceresidues; treating the workpiece, including the exposed metal surfaces,with a solution comprising an aluminum-containing constituent, thesolution reacting at the exposed metallized surfaces to form ananti-corrosive layer over said exposed metal surfaces, said solutionfurther acting as a solvent for removal of said residues from saidworkpiece.
 12. A method as set forth in claim 11 wherein the surfaceresidues are organic residues.
 13. A method as set forth in claim 12wherein the solution is a water-based, alkaline solution.
 14. A methodas set forth in claim 11 wherein the aluminum-containing constituentcomprises aluminum hydroxide.
 15. A method as set forth in claim 11wherein the solution further comprises a silicon-containing constituent.16. A method as set forth in claim 15 wherein the silicon-containingconstituent comprises silicic acid.
 17. A method as set forth in claim11 wherein the solution forms an aluminosilicate at the mettalizedsurfaces.
 18. A method as set forth in claim 17 wherein the solution isa water-based, alkaline solution.
 19. A method as set forth in claim 18wherein the surface residues are organic residues.